Falls affect millions of people each year and result in significant injuries, particularly among the elderly. In fact, it has been estimated that falls are one of the top three causes of death in elderly people. A fall is defined as a sudden, uncontrolled and unintentional downward displacement of the body to the ground, followed by an impact, after which the body stays down on the ground.
PERS is a system in which help can be assured. By means of Personal Help Buttons (PHBs) the user can push the button to summon help in an emergency. A majority of calls are because the user has fallen. Also, if the user suffers a severe fall (for example by which they get confused or even worse if they are knocked unconscious), the user might be unable to push the button, which might mean that help doesn't arrive for a significant period of time, particularly if the user lives alone. The consequences of a fall can become more severe if the user stays lying for a long time.
Fall detection systems are also available that process the output of one or more movement sensors to determine if the user has suffered a fall. Most existing body-worn fall detection systems make use of an accelerometer (usually an accelerometer that measures acceleration in three dimensions) and they are configured to infer the occurrence of a fall by processing the time series generated by the accelerometer. Some fall detection systems can also include an air pressure sensor, for example as described in WO 2004/114245, for measuring the height, height change or absolute altitude of the fall detection system. On detecting a fall, an alarm is triggered by the fall detection system.
In general, a fall detector tests on features like impact, orientation, orientation change, height change, vertical velocity, and alike. Reliable detection results when the set of computed values for these features is different for falls than for other movements that are not a fall.
Some fall detection systems are designed to be worn as a pendant around the neck of the user, whereas others are designed to be worn on or at the torso (e.g. waist, on a waist belt or in a pocket) or on the limbs of the user, for example at the wrist. However, the wrist is capable of complex movement patterns and has a large range of movement shapes/forms/types, and is also susceptible to non-fall related impacts in which the hand, wrist or arm strikes an object, e.g. furniture or a door frame, during normal movement by the user, which means that existing fall detection methods based on analysing measurements from an accelerometer do not provide a sufficiently high detection rate while minimising the number of false alarms for this type of fall detection system.
Therefore there is a need for a method for detecting falls and a fall detection system that provides increased fall detection reliability, particularly a fall detection system that is worn on the wrist.